Hot-gas engine

ABSTRACT

A hot-gas engine with a heater formed by a number of pipes extending in a cylinder form around a space for gases of combustion. An annular element extending at right angles to the cylinder axis is provided between selected pipes, the element comprising a number of recesses which at least partially surround portions of the pipes with slit-shaped ducts for gases of combustion to flow between the walls of the recesses and the relative pipe parts.

United States Patent 1191 Neelen 1 HOT-GAS ENGINE [76] Inventor: Gregorius Theodorus Maria Neelen,

Emmasingel, Eindhoven, Netherlands [22] Filed: Mar. 22, 1971 211 App]. No.: 126,591

[30] Foreign Application Priority Data Apr. 20, 1970 Netherlands 7005791 [52] US. Cl ....I ...6075 l 7, 1117/98 R, 12 27510 [51] Int. Cl. F02g 1/04 [58] Field of Search 165/162; 122/510; 110/98 R; 60/24 [56] References Cited UNITED STATES PATENTS 2,534,208 12/1950 Reed et al 110/98 R 2,752,897 7/1956 Mekler 110/98 R X 2,922,386 1/1960 Endter 110/98 R 3,242,910 3/1966 Hale 110/98 R X Sept. 25, 1973 3,160,145 12/1964 Miller .1 1lO/98 R X 3,055,349 9/1962 Hamilton et a1. 122/510 3,492,813 2/1970 Meijer 60/24 FOREIGN PATENTS OR APPLICATIONS 74,296 1960 France 122/510 Primary Examiner-Martin P. Schwadron Assistant Examiner-Allen M. Ostrager Att0rney-Frank R. Trifari [5 7] ABSTRACT A hot-gas engine with a heater formed by a number of pipes extending in a cylinder form around a space for gases of combustion. An annular element extending at right angles to the cylinder axis is provided between se lected pipes, the element comprising a number of recesses which at least partially surround portions of the pipes with slit-shaped ducts for gases of combustion to flow between the walls of the recesses and the relative pipe parts.

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PATENTED SEP25|975 sum 1 [IF 5 INVENTOR. GREGORIUS T M .NEELEN AGENT PATENTED 2 3.760.592

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INVENTOR.

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AGENT PATENTED $EP25 I973 3. 760 592 sum 5 0F 5 INVENTOR.

GREGORIUS T M.NEELEN mi /mmL We AGENT The invention relates to a hot-gas engine comprising at least one compression space of variable volume and lower average temperature, and at least one expansion space of likewise variable volume and higher average temperature communicating with the compression space, and with a working gas cycled between these spaces. A cooler, a regenerator and a heater are present in the communication between said spaces, the heater being formed by a number of pipes arranged as a cylinder around a space for combustion gases and extending mainly parallel to the cylinder axis. These pipes are alternately spaced, the first pipes communicating at one end with the regenerator and being in open communication at the other and with the second pipes which communicate with the expansion space via inwardly bent ends. Such a hot-gas engine is known, for example, from Dutch Pat. No. 99,795 and UK. Pat. No. 1,053,052.

In such engines the combustion gases flow along the heater pipes while giving off thermal energy to said pipes. In the part of the heater which is constituted by the parts of the first and second pipes extending mutually in parallel, the gases of combustion flow through the narrow passages between said pipes so that a good heat transfer is ensured. At the area where the second pipes are bent inwardly, rather large passage are pres ent between the first and the second pipes as a result of the bending. A part of the hot gases of combustion flows through said rather large passage substantially without giving off thermal energy to the parts of the first and the second pipes forming the large passage. It is the object of the present invention to provide a hotgas engine in which the area of the heater pipes which contributes effectively to the heat transfer is considerably enlarged.

In order to achieve the objective, the hot-gas engine according to the invention is characterized in that at the area where the second pipes are bent inwardly, from the cylinder an annular element extending at right angles to the cylinder axis is arranged between the bent parts of the pipes and the relative parts of the straight first pipes, said element comprising a number of recesses which surround and are spaced from said parts of the first and second pipes, so that slit-shaped flow ducts for gases of combustion are present between the walls of the recesses and the relative pipe parts.

By providing the annular element, the gases of combustion are compelled to flow through the slit-shaped ducts formed between said element and the parts of the first and second pipes. This ensures a good heat transfer between the gases of combustion and said pipe parts, so that in this case the whole pipe length of the heater is used.

During operation of the hot-gas engine, the heater assumes a temperature which may exceeds 700 C. The annular element is then subjected to a considerable thermal expansion and, dependent upon the connection, to thermal stresses. All this may give rise to difficulties, for example, cracks in the annular element, leakage of the heater pipes, and the like. In order to prevent this, the annular element in a further favourable embodiment of the hot-gas engine according to the invention, is subdivided into a number of separate segments. At the high heater temperatures, each segment will now show a small absolute expansion, which will neither produce large thermal stresses at the area where said segment is secured, nor be of influence on the other segments which, actually, are separated from it. The segments may be connected, for example, to the first or to the second pipes.

In a hot-gas engine known from MTZ- Motertechnische Zeitschrift 29 Nr. 7, July, 1968 (FIG. 13), a sleeve consisting of a heat-conducting material and provided with fins is arranged around each of the ends of the first pipes communicating with the regenerator so as to ensure a good heat transfer between said pipe ends and the gases of combustion flowing past said pipes. In a further favourable embodiment of the hot-gas engine according to the invention, the segments and the sleeves form one assembly and are manufactured from the same material.

This presents the advantage that the sleeve and the segments can be manufactured simultaneously and together in one manufacturing process, for example moulding, and that assembly can be carried out in one operation which is economically very attractive. During operation of the engine, the temperature of said ring segment also does not increase too high owing to the thermal connection between the ring segment and the sleeve which reduces the danger of corrosion.

In order that the invention may be readily carried into effect, two embodiments of the hot-gas engine according to the invention (FIGS. 1a and 2a) will now be described in greater detail, by way of example, with reference to the accompanying diagrammatic drawings which are not drawn to scale.

Reference numeral 1 in FIG. 1a denotes a cylinder in which a piston 2 and a displacer 3 can move with a phase difference. The piston 2 and the displacer 3 are connected to a driving mechanism (not shown) by means of a piston rod 4 and a displacer rod 5, respectively. Between the piston 2 and the displacer 3 there is a compression space 6 which communicates with an expansion space 10 above the displacer via a cooler 7, a regenerator 8 and a heater 9. The heater 9 is constituted by a wreath of pipes arranged around a space 1 1 for gases of combustion.

Furthermore are present a conventional burner device (not shown) for providing hot combustion gases in a well known manner. Conduit 15 is an exhaust for said gases of combustion.

The heater 9 consists of a number of first pipes 16 which communicate at one end the near end 160, with the regenerator 8 and at the other end, the remote end 16b open into an annular duct 17, and a number of second pipes 18, arranged alternately between the first pipes 16 and having a remote end 18b communicating the annular duct 17 with the expansion space 10. For clarity, only two sets of first and second pipes are shown. During operation of the hot-gas engine, the hotgases of combustion originating from the burner device flow past the first pipes 16 and second pipes 18 while giving off thermal energy to said pipes and leave the engine via exhaust 15. Between the parts of the first pipes 16 and second pipes 18 extending vertically beside each other, narrow passages are present so that a good heat transfer is ensured there between the past-flowing gases of combustion and the said pipe parts.

At the area where the second pipes 18 are bent inwardly, comparatively large passages are present between the inwardly extending lowermost parts of the second pipes 18 and the straight lowermost parts of the first pipes 16 owing to said bends. In order to obtain, at this area also, a good heat transfer between the gases of combustion and the said lowermost pipe parts, a ring 20 is provided which extends at right angles to the vertically extending first pipes 16 and which comprises recesses which surround the lowermost parts of the first pipes 16 and the second pipes 18 partly and with some space from these parts in such manner that slit-shaped flow ducts for gases of combustion are present between the walls of said recesses and the said pipe parts. The gases of combustion from the space 11 are now compelled to flow through said slit-shaped flow ducts, as a result of which a good heat transfer is ensured also between the gases of combustion and the lowermost parts of the pipes 16 and 18. All this is illustrated in detail in FIG. lb which shows a first pipe 16 and a second pipe 18 in combination with a part of the ring 20. The ring or annular element 20 may, for example, be moulded or punched from sheet material and be provided with recesses after punching.

Since during operation of the hot-gas engine the heater 9 assumes a temperature of 700 C or higher, the

- ring 20 will experience a considerable thermal expansion. When the ring is secured to the pipes 16 and/or 18, stresses in the material may occur due to said expansion, notably at the area of the connection, as a possible result of which cracks in ring 20 and, which is much more serious, leakage of the heater pipes 16 and 18 may occur so that working medium escapes from the engine. In order to prevent this, the ring may be divided into a number of independent segments 20' spaced circumferentially which each have a comparatively small absolute expansion and consequently give hardly rise to material stresses. Such a ring segment may be constructed as is shown in FIG. 1b.

FIG. 2a shows a hot-gas engine which generally is similar to that shown in FIG. 1 and in which therefore corresponding components are referred to by the same reference numerals. 1

In the present hot-gas engine, a sleeve 21 of a heat conducting material which is provided with fins is arranged around each of the ends of the first pipes 16 communicating with the regenerator 8. The gases of combustion first flow past the uppermost parts of the first pipes 16 and past second pipes 18, respectively, and then past the lowermost parts or sections 160 of pipes 16, so that a good heat exchange is ensured by the sleeves 21. At he area where second pipes 18 are bent inwardly, ring segments 20' are arranged between the bending pipe parts and the relative straight parts of first pipes 16, which segments form one assembly with the sleeves 21 and are manufactured from the same material. FIGS. 2b and 20 show embodiments of such a combination of sleeve-ring segments. By the recesses in the ring segments 20', which recesses again surround the relative pipe parts partly and with some play, the gases of combustion are again compelled to flow through the slit-shaped ducts between the walls of said recesses and the relative pipe parts and an intimate contact with the gases of combustion and hence a large heat transfer is ensured for these pipe parts also.

By constructing the sleeves 21 and the ring segments 20' as one assembly of the same material, on the one hand the advantage of a comparatively cheap manufacture is obtained, because the combination can, for example, be moulded in one operation. On the other hand, the assembly of the combination instead of the two separate components is time-saving. Since in addition the ring segments are thermally connected to the sleeves, the temperature of said segments during operation of the engine does not rise too high and the danger of corrosion is reduced.

It will be obvious from the above that the invention provides a hot-gas engine in which the whole available surface area of the heater pipes is efficiently used in the heat transfer of the gases of combustion to the heater of the engine.

Iclaim:

1. In a hot-gas engine having one variable-volume compression space and one variable-volume expansion space in communication and respectively operable at lower and higher average temperatures, and communicating between said compression and expansion spaces a cooler, a regenerator, and a heater heated by a heating medium and through which flows a working me dium, the heater comprising a plurality of first pipes positioned generally parallel to define a cylinder, these pipes having near ends in communication with the regenerator and remote ends, a plurality of second pipes each positioned generally parallel to and between two of said first pipes, the second pipes having remote ends in communication with the remote ends of said first pipes, and having near ends bent inwardly of said cylinder, communicating with said expansion space, and defining an annular space between said near ends of said first and second pipes, the heater further comprising a plurality of elements positioned generally in said annular space and spaced from the near ends of said first and second pipes each element separating the near ends of two adjacent first and second pipes and defining a flow duct therebetween for increasing the flow of said heating medium in said ducts.

2. Apparatus according to claim 1 wherein said annular element comprises a plurality of segments positioned circumferentially.

3. Apparatus according to claim 2 wherein each of said first pipes has a lower section extending from its near end connection with the regenerator to said annular element, said apparatus further comprising a sleeve of heat-conducting material covering each of said lower sections, each sleeve including transverse heatexchange fins.

4. Apparatus according to claim 3 wherein each of said segments of said annular element is secured to one sleeve.

73 g UNITED STATES PATENT-OFFICE CERTIFICATE OF CORRECTION A A 3 v Patent No. Dated A September 1973 Inventor(s) GREGORIUS THEODORUS MARIA NEELEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

After the inventors name, insert the assigneev I U.,S PHILIPS CORPORATIO Signed] and sealed this 12th day of March 197A.

' (SEAL) Attest:

EDWARD M.,FLETCHEB,JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,76 9 Dated September 25, 1973 Inventor) GREGORIUS THEODORUS MARIA NEELEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Change the Foreign Application Priority Data to --April 21', 197o--.

Signed and sealed this 21st day of May 197A.

(SiFJAL) Atteat: I

EDWARD M.FLE'I'CiL-IR,JH. I G. I-IARSHALL DANN Attesting Officer Commissioner of Patents 

1. In a hot-gas engine having one variable-volume compression space and one variable-volume expansion space in communication and respectively operable at lower and higher average temperatures, and communicating between said compression and expansion spaces a cooler, a regenerator, and a heater heated by a heating medium and through which flows a working medium, the heater comprising a plurality of first pipes positioned generally parallel to define a cylinder, these pipes having near ends in communication with the regenerator and remote ends, a plurality of second pipes each positioned generally parallel to and between two of said first pipes, the second pipes having remote ends in communication with the remote ends of said first pipes, and having near ends bent inwardly of said cylinder, communicating with said expansion space, and defining an annular space between said near ends of said first and second pipes, the heater further comprising a plurality of elements positioned generally in said annular space and spaced from the near ends of said first and second pipes each element separating the near ends of two adjacent first and second pipes and defining a flow duct therebetween for increasing the flow of said heating medium in said ducts.
 2. Apparatus according to claim 1 wherein said annular element comprises a plurality of segments positioned circumferentially.
 3. Apparatus according to claim 2 wherein each of said first pipes has a lower section extending from its near end connection with the regenerator to said annular element, said apparatus further comprising a sleeve of heat-conducting material covering each of said lower sections, each sleeve including transverse heat-exchange fins.
 4. Apparatus according to claim 3 wherein each of said segments of said annular element is secured to one sleeve. 